Cocoa wrapper around C++ code, what is the best idiom for wrapping STL style iterators?

I am writing a Cocoa front end for Xapian ( www.xapian.org )
This is my first real Cocoa app and I have struggling with how to represent
the sytle iterators that Xapian uses.
I tried using NSEnumerator subclasses how would you do them?

> This is my first real Cocoa app and I have struggling with how to represent
> the sytle iterators that Xapian uses.
> I tried using NSEnumerator subclasses how would you do them?

When? Where? Why?

I use C++/STL from Cocoa all the time, and have no need for NSEnumerator.
For instance, if you wish to display an NSTableView, in the data source's
callback just use the C++ container directly. So we'd need more detailed
questions to offer any useful help.